Here's a fabulous and long article on the Emergent Church. If you want to just jump to the bottom of the article and read the Four Areas of Concern you will be most blessed. Tony Jones in his blog said he felt this was an even-handed presentation of the Emergent Church. I think it summarizes the Emergent Church's beliefs and also reveals some key areas of danger: The Article Found Here
Though I've only read a few books and a few articles on both sides of the Emergent debate, I stand behind the conclusions of this author, Justin Taylor.